The 225(& later 198) are built on the RG tall-deck block, the 170 is built on the G short-deck block, the difference in deck height is just short of 1& 5/8". It's not that much in the vertical, but still over an inch, that simply raises both manifolds(&/or headers) that same amount together. The relationship to the hood up top, & position of the exhaust below are the real issues, that is why 225 headers hang too low on a 170 in-chassis.